Frequency Division Multiplexing with Polyphase Shifters

ABSTRACT

This document describes techniques and systems for frequency division multiplexing (FDM) with polyphase shifters. A radar system can include transmitters, receivers, polyphase shifters, and a processor. The transmitters emit electromagnetic (EM) signals in an FDM scheme, and the receivers detect EM signals reflected by objects. The received EM signals include multiple channels. The processor controls the polyphase shifters to introduce phase shifts to the EM signals. The processor can also divide a Doppler-frequency spectrum of the received EM signals into multiple sectors representing a respective frequency range. Each channel is associated with a respective sector. The processor can determine, using non-coherent integration across the sectors, potential detections of the objects, including aliased and actual detections. The processor can then determine the actual detections. In this way, the described FDM techniques with polyphase shifters can resolve Doppler ambiguities in received EM signals.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit under 35 U.S.C. 119(e) of U.S.Provisional Application No. 63/156,480, filed Mar. 4, 2021, thedisclosure of which is incorporated by reference in its entirety herein.

BACKGROUND

Radar systems transmit and receive electromagnetic (EM) signals fordetecting and tracking objects. In automotive applications, radarsystems provide information about the vehicle's environment and can playan essential role in Advanced Driver Assistance Systems (ADAS). Highlyautomated systems generally require radar data with high resolution inrange, Doppler, and angular dimensions. Popular approaches to achieveimproved angular dimensions are multiple-input and multiple-output(MIMO) radar techniques that provide relatively large virtual arrayswith reduced angular ambiguity. MIMO techniques, however, can provideinadequate Doppler discrimination.

SUMMARY

This document describes techniques and systems for frequency divisionmultiplexing (FDM) with polyphase shifters. In some examples, a radarsystem for installation on a vehicle includes multiple transmitters,multiple receivers, multiple polyphase shifters, and a processor. Thetransmitters can transmit electromagnetic (EM) signals in an FDM scheme.The receivers can receive EM signals reflected by one or more objectsthat include multiple channels. The polyphase shifters can introduce atleast three potential phase shifts to the transmitted EM signals,received EM signals, or both. The polyphase shifters are operablyconnected to the transmitters, receivers, or a combination of both. Theprocessor can control the polyphase shifters to introduce phase shifts.The processor can also divide a Doppler-frequency spectrum of thereceived EM signals into multiple sectors representing a respectivefrequency range. Each channel is associated with a respective sector.The processor can determine, using non-coherent integration of thereceived EM signals across the sectors, potential detections of theobjects. The processor can then determine the actual detections. In thisway, the described FDM techniques with polyphase shifters can resolveDoppler ambiguities in received EM signals.

This document also describes methods performed by the above-summarizedsystem and other configurations of the radar system set forth herein andmeans for performing these methods.

This Summary introduces simplified concepts related to enabling FDMtechniques with polyphase shifters in a radar system, which are furtherdescribed in the Detailed Description and Drawings. This Summary is notintended to identify essential features of the claimed subject matter,nor is it intended for use in determining the scope of the claimedsubject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

The details of one or more aspects of slow-time frequency divisionmultiplexing with polyphase shifters are described in this document withreference to the following figures. The same numbers are often usedthroughout the drawings to reference like features and components:

FIG. 1 illustrates an example environment in which a radar system canuse FDM with polyphase shifters in accordance with techniques of thisdisclosure;

FIG. 2 illustrates an example configuration of a radar system using FDMwith polyphase shifters within a vehicle in accordance with techniquesof this disclosure;

FIGS. 3, 4-1, 4-2, 5-1, and 5-2 illustrate example conceptual diagramsof a radar system that uses FDM with polyphase shifters;

FIG. 6 illustrates an example diagram of transmitted EM signals usingFDM with polyphase shifters;

FIG. 7 illustrates an example graph of a received EM signal of a radarsystem using FDM with polyphase shifters in a Doppler binrepresentation;

FIG. 8 illustrates an example method for a radar system that uses FDMwith polyphase shifters to determine a Doppler frequency of obj ects;

FIGS. 9-11 illustrate example graphical representations of theassociation of channels and sectors in a radar system using FDM withpolyphase shifters; and

FIGS. 12-17 illustrate example flowcharts for a radar system that usesFDM with polyphase shifters to perform non-coherent integration anddetermine actual detections associated with objects.

DETAILED DESCRIPTION

Overview

Radar systems can be configured as an important sensing technology thatvehicle-based systems use to acquire information about the surroundingenvironment. For example, vehicle-based systems can use radar systems todetect objects in or near a roadway and, if necessary, take necessaryactions (e.g., reduce speed, change lanes) to avoid a collision.

Radar systems generally include at least two antennas to transmit andreceive radar (e.g., EM) signals. Many vehicle-based systems requirehigh resolution in range, Doppler frequency, and angle. These systemsalso require accurate discrimination between multiple targets withsimilar ranges or Doppler frequencies. Design engineers often addressthese requirements by including more antenna channels in radar systems.For example, some automotive radar systems operate MIMO radars toincrease the number of channels and improve angular resolution. A MIMOradar system with three transmit channels and four receive channels canform a virtual array (also referred to as a “synthetic array”) of twelvechannels. With additional channels, a MIMO radar system can operate withan improved angular resolution, relying on a flexible physical layout ofinexpensive and possibly fewer hardware components than traditionalnon-MIMO radar systems.

MIMO radar systems generally use orthogonal waveforms to transmit andreceive independent, orthogonal EM signals and identify or separate thedifferent channels. Radar systems can implement orthogonal waveforms invarious ways, including using time-division multiplexing (TDM), FDM, andcode multiplexing (CM) techniques. However, each orthogonal waveformtechnique has associated benefits and weaknesses.

For example, FDM techniques generally place signals from transmitchannels in different frequency bands by adding frequency offsets to thetransmit signals. Such techniques generally operate in a fast-time(range) domain, introduce a range-dependent phase offset among channels,and reduce range coverage. FDM techniques can also require a highersampling rate due to the increased intermediate-frequency bandwidth.

CM techniques can enable simultaneous transmission and operate infast-time (e.g., within a chirp, range domain) and slow-time domains(e.g., chirp to chirp, Doppler domain). CM techniques generally recovera signal matching a current code by suppressing energy from other codedsignals. The distributed EM energy left from the suppressed signals isgenerally considered residue or noise and limits the dynamic range ofthe radar system. A smaller dynamic range limits the radar system'sability to differentiate smaller objects from larger objects.

Some TDM techniques do not support simultaneous transmission. Instead,individual transmitters transmit sequentially, leading to lessinterference between transmit channels and a maximum degree oforthogonality. Such techniques, however, generally do not provide thesignal-to-noise ratio benefits realized with simultaneous transmission(e.g., FDM and CM techniques) and can lead to Doppler ambiguity amongchannels.

Previously used techniques, including those described above, generallydo not provide adequate discrimination among channels, leading to asmaller signal-to-noise ratio. In contrast, this document describestechniques and systems to provide a radar system that achievessimultaneous transmission using FDM techniques with polyphase shifters.In this way, the described techniques and systems support multipletransmitters transmitting simultaneously with accurate recovery andwithout Doppler ambiguity. For example, a vehicle's radar systemincludes multiple transmitters, multiple receivers, multiple polyphaseshifters, and a processor. The transmitters can transmit EM signals inan FDM scheme. The receivers can receive EM signals reflected by one ormore objects that include multiple channels. The polyphase shifters canintroduce at least three potential phase shifts to the transmitted EMsignals, received EM signals, or both. The polyphase shifters areoperably connected to the transmitters, receivers, or a combination ofboth. The processor can control the polyphase shifters to introducephase shifts. The processor can also divide a Doppler-frequency spectrumof the received EM signals into multiple sectors representing arespective frequency range. Each channel is associated with a respectivesector. The processor can determine, using non-coherent integration ofthe received EM signals across the sectors, potential detections of theobjects. The processor can then determine the actual detections. In thisway, multiple transmitters transmitting simultaneously with accuraterecovery and without Doppler ambiguity are supported. Accurate recoveryis possible by avoiding interference among channels. The described FDMtechniques avoid ambiguity by identifying each channel withoutadditional information.

This example is just one example of the described techniques and systemsof a radar system using slow-time frequency division multiplexing withpolyphase shifters. This document describes other examples andimplementations.

Operating Environment

FIG. 1 illustrates an example environment 100 in which a radar system104 can use FDM with polyphase shifters 116 in accordance with thetechniques of this disclosure. In the depicted environment 100, theradar system 104 is mounted to, or integrated within, a vehicle 102traveling on a roadway 106. Within a field-of-view 108, the radar system104 can detect one or more objects 110 in the vicinity of the vehicle102.

The radar system 104 can detect one or more objects 110 in the vicinityof the vehicle 102. Although illustrated as a sedan, the vehicle 102 canrepresent other types of motorized vehicles (e.g., a car, an automobile,a truck, a motorcycle, a bus, a tractor, a semi-trailer truck),non-motorized vehicles (e.g., a bicycle), railed vehicles (e.g., atrain), watercraft (e.g., a boat), aircraft (e.g., an airplane), orspacecraft (e.g., satellite). In general, manufacturers can mount theradar system104 to any moving platform, including moving machinery orrobotic equipment.

In the depicted implementation, the radar system 104 is mounted on thefront of the vehicle 102 and illuminates the object 110. The radarsystem 104 can detect the object 110 from any exterior surface of thevehicle 102. For example, vehicle manufacturers can integrate the radarsystem 104 into a bumper, side mirror, headlights, rear lights, or anyother interior or exterior location where the object 110 requiresdetection. In some cases, the vehicle 102 includes multiple radarsystems 104, such as a first radar system 104 and a second radar system104, that provide a larger instrument field-of-view 108. In general,vehicle manufacturers can design the locations of the radar systems 104to provide a particular field-of-view 108 that encompasses a region ofinterest. Example fields-of-view 108 include a 360-degree field-of-view,one or more 180-degree fields-of-view, one or more 90-degreefields-of-view, and so forth, which can overlap or be combined into afield-of-view 108 of a particular size.

The object 110 is composed of one or more materials that reflect radaror EM signals. Depending on the application, the object 110 canrepresent a target of interest. In some cases, the object 110 can be amoving object (e.g., another vehicle) or a stationary object (e.g., aroadside sign, road barrier, debris). Depending on the application, theobject 110 can represent a target of interest from which the vehicle 102can safely navigate the roadway 106.

The radar system 104 emits EM radiation by transmitting EM signals orwaveforms via antenna elements. For example, in the environment 100, theradar system 104 can detect and track the object 110 by transmitting andreceiving one or more EM signals. For example, the radar system 104 cantransmit EM signals between one hundred and four hundred gigahertz(GHz), between four and one hundred GHz, or between approximatelyseventy and eighty GHz.

The radar system 104 can be a MIMO radar system that can match thereflected EM signals to corresponding objects 110. The radar system 104can also operate as a traditional radar system that does not rely onMIMO techniques. The radar system 104 can include a transmitter 112 totransmit EM signals. The radar system 104 can also include a receiver114 to receive reflected versions of the EM signals. The transmitter 112includes one or more components, including an antenna or antennaelements, for emitting the EM signals. The receiver 114 includes one ormore components, including an antenna or antenna elements, for detectingthe reflected EM signals. The transmitter 112 and the receiver 114 canbe incorporated together on the same integrated circuit (e.g., atransceiver integrated circuit) or separately on different integratedcircuits. In other implementations, the radar system 104 does notinclude a separate antenna, but the transmitter 112 and the receiver 114each include one or more antenna elements.

The radar system 104 can also include the polyphase shifters 116. Thepolyphase shifters 116 are respectively associated with and operablyconnected to the transmitter 112, the receiver 114, or both. Thepolyphase shifters 116 can apply a phase shift to one or more signalpulses of the EM signal transmitted by the transmitter 112 in someapplications. In other implementations, the polyphase shifters 116 canapply a phase shift to one or more signal pulses of the reflected EMsignal received by the receiver 114. In yet other implementations, thepolyphase shifters 116 can apply a phase shift to both the transmittedEM signals and the received EM signals.

The radar system 104 also includes one or more processors 118 (e.g., anenergy processing unit) and computer-readable storage media (CRM) 120.The processor 118 can be a microprocessor or a system-on-chip. Theprocessor 118 can execute instructions stored in the CRM 120. Forexample, the processor 118 can process EM energy received by thereceiver 114 and determine, using a spectrum analysis module 122 andnon-coherent integrator 124, the location of the object 110 relative tothe radar system 104. The processor 118 can also detect various features(e.g., range, target angle, range rate, velocity) of the object 110. Theprocessor 118 can include instructions or be configured to control thetransmitter 112, the receiver 114, and the polyphase shifters 116. Theprocessor 118 can also generate radar data for at least one automotivesystem. For example, the processor 118 can control, based on processedEM energy from the receiver 114, an autonomous or semi-autonomousdriving system of the vehicle 102.

The spectrum analysis module 122 allows for multiple channels in thereceived EM signals to resolve Doppler ambiguities among the received EMsignals. In particular, the spectrum analysis module 122 can divide aDoppler-frequency spectrum of the received EM signals into severalsectors. The sectors represent a respective frequency range within theDoppler-frequency spectrum. For example, the spectrum analysis module122 can generate more sectors than the number of channels and equallysize the sectors. As another example, the spectrum analysis module 122can generate the same number of sectors as channels and unequally sizethe sectors (e.g., each sector has a different frequency width). As yetanother example, the spectrum analysis module 122 can generate the samenumber of sectors as channels and size the sectors with a subset ofequally sized sectors and another subset of unequally sized sectors. TheDetailed Description describes the generation of the sectors andassociation of channels to sectors in greater detail with respect toFIGS. 9 through 11. The radar system 104 can implement the spectrumanalysis module 122 as instructions in the CRM 120, hardware, software,or a combination thereof executed by the processor 118.

The non-coherent integrator 124 can process EM energy received by thereceiver 114 to identify the objects 110 and resolve Doppler ambiguitiesregarding the objects 110 within the field-of-view 108 of the radarsystem 104. The non-coherent integrator 124 can use several schemes toreject aliased detections and resolve Doppler ambiguities. The schemesused by the non-coherent integrator 124 can include single-channeldetection and dealiasing, circular shifting and minimum analysis,summation and carrier knowledge, sector-based integration and maximumanalysis, and circular shifting and minimum and maximum analysis, asdescribed in greater detail with respect to FIGS. 12 through 17. Theradar system 104 can implement the non-coherent integrator 124 asinstructions in the CRM 120, hardware, software, or a combinationthereof executed by the processor 118.

The described radar system 104 can facilitate the simultaneoustransmission of multiple transmitter channels for a MIMO radar systemwith polyphase shifters 116. The described aspects of FDM with polyphaseshifters support multiple transmitters 112 transmitting simultaneouslywith accurate recovery and without Doppler ambiguity. Accurate recoveryis possible because interference among channels is avoided using thespectrum analysis module 122. Doppler ambiguity is resolved using thenon-coherent integrator 124 to reject aliased detections.

As an example environment, FIG. 1 illustrates the vehicle 102 travelingon the roadway 106. The radar system 104 detects the object 110 in frontof the vehicle 102. The radar system 104 can define a coordinate systemwith an x-axis (e.g., in a forward direction along the roadway 106), anda y-axis (e.g., perpendicular to the x-axis and along a surface of theroadway 106), in some cases, further defining a z-axis (e.g., normal tothe x-y plane defined by the x and y axis). The transmitter 112 of theradar system 104 can transmit EM signals in front of the vehicle 102.The object 110 can reflect the transmitted EM signals as reflected EMsignals. The receiver 114 can detect the reflected EM signals.

The vehicle 102 can also include at least one automotive system thatrelies on data from the radar system 104, such as a driver-assistancesystem, an autonomous-driving system, or a semi-autonomous-drivingsystem. The radar system 104 can include an interface to an automotivesystem that relies on the data. For example, via the interface, theprocessor 118 outputs a signal based on EM energy received by thereceiver 114.

Generally, the automotive systems use radar data provided by the radarsystem 104 to perform a function. For example, the driver-assistancesystem can provide blind-spot monitoring and generate an alert thatindicates a potential collision with the object 110 that is detected bythe radar system 104. The radar data from the radar system 104 indicateswhen it is safe or unsafe to change lanes in such an implementation. Theautonomous-driving system may move the vehicle 102 to a particularlocation on the roadway 106 while avoiding collisions with the object110 detected by the radar system 104. The radar data provided by theradar system 104 can provide information about the distance to and thelocation of the object 110 to enable the autonomous-driving system toperform emergency braking, perform a lane change, or adjust the speed ofthe vehicle 102.

FIG. 2 illustrates an example configuration of a radar system using FDMwith polyphase shifters within the vehicle 102 in accordance with thetechniques of this disclosure. The vehicle 102 can include drivingsystems 206, including an autonomous driving system 208 orsemi-autonomous driving system 210, that use radar data from the radarsystem 104 to control the vehicle 102. As described with respect to FIG.1, the vehicle 102 can include the radar system 104.

The vehicle can also include one or more sensors 202, one or morecommunication devices 204, and the driving systems 206. The sensors 202can include a location sensor, a camera, a lidar system, or acombination thereof. The location sensor, for example, can include apositioning system that can determine the position of the vehicle 102.The camera system can be mounted on or near the front of the vehicle102. The camera system can take photographic images or video of theroadway 106. In other implementations, a portion of the camera systemcan be mounted into a rear-view mirror of the vehicle 102 to have afield-of-view of the roadway 106. In yet other implementations, thecamera system can project the field-of-view from any exterior surface ofthe vehicle 102. For example, vehicle manufacturers can integrate atleast a part of the camera system into a side mirror, bumper, roof, orany other interior or exterior location where the field-of-view includesthe roadway 106. The lidar system can use electromagnetic signals todetect the objects 110 (e.g., other vehicles) on the roadway 106. Datafrom the lidar system can provide an input to the spectrum analysismodule 122 or the non-coherent integrator 124. For example, the lidarsystem can determine the traveling speed of a vehicle in front of thevehicle 102 or nearby vehicles traveling in the same direction as thevehicle 102.

The communication devices 204 can be radio frequency (RF) transceiversto transmit and receive RF signals. The transceivers can include one ormore transmitters and receivers incorporated together on the sameintegrated circuit (e.g., a transceiver integrated circuit) orseparately on different integrated circuits. The communication devices204 can be used to communicate with remote computing devices (e.g., aserver or computing system providing navigation information or regionalspeed limit information), nearby structures (e.g., construction zonetraffic signs, traffic lights, school zone traffic signs), or nearbyvehicles. For example, the vehicle 102 can use the communication devices204 to wirelessly exchange information with nearby vehicles usingvehicle-to-vehicle (V2V) communication. The vehicle 102 can use V2Vcommunication to obtain the speed, location, and heading of nearbyvehicles. Similarly, the vehicle 102 can use the communication devices204 to wirelessly receive information from nearby traffic signs orstructures to indicate a temporary speed limit, traffic congestion, orother traffic-related information.

The communication devices 204 can include a sensor interface and adriving system interface. The sensor interface and the driving systeminterface can transmit data over a communication bus of the vehicle 102,for example, between the radar system 104 and the driving systems 206.

The vehicle 102 also includes at least one driving system 206, such asthe autonomous driving system 208 or the semi-autonomous driving system210, that relies on data from the radar system 104 to control theoperation of the vehicle 102 (e.g., set the driving speed or avoid theobject 110). Generally, the driving systems 206 use data provided by theradar system 104, specifically the non-coherent integrator 124, and/orthe sensors 202 to control the vehicle 102 and perform certainfunctions. For example, the semi-autonomous driving system 210 canprovide adaptive cruise control and dynamically adjust the travel speedof the vehicle 102 based on the presence of the object 110 in front ofthe vehicle 102. In this example, the data from the non-coherentintegrator 124 can identify the object 110 and its speed in relation tothe vehicle 102.

The autonomous driving system 208 can navigate the vehicle 102 to aparticular destination while avoiding the obj ect 110 as identified bythe non-coherent integrator 124 and/or the radar system 104. The dataprovided by the radar system 104 about the object 110 can provideinformation about the location and/or speed of the obj ect 110 to enablethe autonomous driving system 208 to adjust the speed of the vehicle102.

Example Configurations

FIG. 3 illustrates an example conceptual diagram 300 of a radar system302 that uses FDM with polyphase shifters 308. For example, the radarsystem 302 can be the radar system 104 of FIGS. 1 and 2. The conceptualdiagram 300 illustrates components of the radar system 302 as distinctcomponents, but some or all of them may be combined into a smallersubset of distinct components.

In the depicted implementation, the radar system 302 includes multipletransmitters 304, which are illustrated as antenna elements in thisexample, configured to transmit respective EM signals. The radar system302 uses the transmitted EM signals to detect any objects 110 in thevicinity of the vehicle 102 within the field-of-view 108. Thetransmitters 304 can transmit a linear frequency-modulated signal (e.g.,chirping signal) in some implementations. In other implementations, thetransmitters 304 can transmit a phase-modulated continuous wave (PMCW)signal or a pulse signal (e.g., unmodulated signal). The transmitted EMsignals can be any viable signal use for a radar system. The radarsystem 302 also includes multiple receivers 306, which are illustratedas antenna elements in this example, configured to receive reflected EMsignals reflecting by the objects 110.

The radar system 302 includes a processor and CRM, which can be theprocessor 118 and the CRM 120 of FIGS. 1 and 2, respectively. The CRMincludes instructions that, when executed by the processor, causes theprocessor to control the transmitters 304 or the phase shifters 308. Forexample, the processor can use the spectrum analysis module 122 tocontrol the phase shift applied or introduced to the transmitted EMsignals.

In the illustrated example, the radar system 302 includes avoltage-controlled oscillator (VCO) 312 operatively coupled to thetransmitters 304. The VCO 312 provides the basis or reference signal forEM signals transmitted by the transmitters 304. The multiple polyphaseshifters 308 are respectively associated with the transmitters 304 andcoupled to the transmitters 304 and the VCO 312. In the depictedimplementation, a phase shifter 308 is operatively coupled to eachtransmitter 304. In other implementations, a phase shifter 308 can beoperatively coupled to fewer than each transmitter 304.

The polyphase shifters 308 can control a phase shift applied orintroduced to one or more EM signal pulses transmitted by thetransmitters 304. Each polyphase shifter 308 has multiple potentialoutput stages (e.g., 4, 8, 16, 32, or 64 stages). For example, theprocessor can provide a polyphase control signal 310 to the polyphaseshifters 308 to control or set the phase stage of each polyphase shifter308. The polyphase control signal 310 can be a multiple-bit signal(e.g., 2-bit, 3-bit, 4-bit, 5-bit, or 6-bit), allowing the polyphaseshifters 308 to have more than two phase stages. The increased number ofpotential phase stages provides more flexibility in an FDM coding schemeapplied by the radar system 302 than binary phase shifters can provide.The polyphase control signal 310 can add a progressive phase modulationϕ to the transmitted EM signal pulses, which shifts the frequency orDoppler frequency of the reflected EM signals by an offset frequencyω_(c), which is equal to the product of two, pi, and the phasemodulation (e.g., ω_(c)=2πϕ).

As described above, the receivers 306 receive reflected EM signals. Theradar system 302 processes the received EM signals to make one or moredeterminations regarding objects 110 within the field-of-view 108 of theradar system 302. The receivers 306 are operatively coupled torespective low noise amplifiers (LNAs) 314. The LNAs 314 can amplify thereceived EM signal without significant degradation to thesignal-to-noise ratio. The LNAs 314 are operatively coupled torespective mixers 316, which are coupled to the VCO 312. The output ofthe VCO 312 serves as a reference signal and combines with therespective received EM signals in the mixers 316. The radar system 302passes the respective received EM signals through band-pass filters(BPFs) 318 and analog-to-digital converters (ADCs) 320 before analyzingthem with a digital signal processor (DSP) 322. The DSP 322 can make oneor more determinations regarding the objects 110, including resolvingDoppler ambiguities. The BPFs 318 can pass frequencies in the receivedEM signals within a specific range and reject or attenuate frequenciesoutside this range. In other implementations, the radar system 302 canuse additional or different filters, including low-pass filters orhigh-pass filters. The ADCs 320 converts the analog EM signals into adigital signal. The DSP 322 can use the non-coherent integrator 124 toresolve Doppler ambiguities and identify the Doppler frequencyassociated with the objects 110. Although the DSP 322 is illustrated asa separate component from the processor, the radar system 302 caninclude a single processor that controls the transmission of EM signalsand makes determinations from the reception of EM signals.

FIGS. 4-1 and 4-2 illustrate other example conceptual diagrams 400 and410 of a radar system 402 and 412, respectively, that uses FDM withpolyphase shifters 308. For example, the radar system 402 and 412 can bethe radar system 104 of FIGS. 1 and 2. The conceptual diagrams 400 and410 illustrate components of the radar system 402 and 412, respectively,as distinct components, but some or all of them may be combined into asmaller subset of distinct components.

The radar systems 402 and 412 include similar components as depicted forthe radar system 302 in FIG. 3. For example, the radar systems 402 and412 include the transmitters 304, receivers 306, a processor, CRM,polyphase shifters 308, VCO 312, LNAs 314, the mixer 316, the BPF 318,the ADC 320, and the DSP 322. The polyphase shifters 308 are operativelycoupled to the LNAs 314 and the mixer 316 in the receiver paths of theradar systems 402 and 412. In FIG. 4-1, the polyphase shifters 308 areoperatively coupled to each receive channel and then operatively coupledto a single down-conversion or analog-to-digital conversion channel. InFIG. 4-2, the polyphase shifters 308 are operatively coupled to eachreceive channel and a subset of the receive channels or polyphaseshifters 308 are then operatively coupled to a down-conversion oranalog-to-digital conversion channel. As illustrated in the conceptualdiagram 410, the radar system 412 includes two polyphase shifters 308 orreceive channels per down-conversion or analog-to-digital conversionchannel. In other implementations, the radar system 412 can includeanother number of polyphase shifters 308 or receive channels perdown-conversion or analog-to-digital conversion channel, resulting in Nreceive groups with M receive channels per receive group.

The polyphase shifters 308 can also be operatively coupled in betweenother components in the receiver paths, including between the receivers306 and the LNAs 314. The polyphase shifters 308 are not operativelycoupled to the transmitters 304 but instead respectively associated withthe receivers 306. The polyphase shifters 308 can introduce or apply aphase shift to the received EM signals. The radar system 402 or 412 cancombine (e.g., super impose) the signals received by one or more of thereceivers 306 prior to analog-to-digital conversion by the ADC 320.

As described above, each polyphase shifter 308 has multiple potentialoutput stages (e.g., 4, 8, 16, 32, or 64 stages). For example, theprocessor 118 can provide the polyphase control signal 310 to thepolyphase shifters 308 to control or set the phase stage of eachpolyphase shifter 308. The polyphase control signal 310 can be amultiple-bit signal (e.g., 2-bit, 3-bit, 4-bit, 5-bit, or 6-bit), givingthe polyphase shifters 308 more than two phase stages. The increasednumber of potential phase stages provides more flexibility in an FDMcoding scheme applied by the radar system 402 or 502 to the received EMsignals than binary phase shifters can provide. The polyphase controlsignal 310 can add a progressive phase modulation ϕ to the received EMsignal pulses, which shifts the frequency or Doppler frequency of thereflected EM signals by an offset frequency ω_(c), which is equal to theproduct of two, pi, and the phase modulation (e.g., ω_(c)=2πϕ).

FIGS. 5-1 and 5-2 illustrate other example conceptual diagrams 500 and510 of a radar system 502 and 512, respectively, that uses FDM withpolyphase shifters 308. For example, the radar system 502 and 512 can bethe radar system 104 of FIGS. 1 and 2. The conceptual diagrams 500 and510 illustrate components of the radar system 502 and 512, respectively,as distinct components, but some or all of them may be combined into asmaller subset of distinct components.

The radar systems 502 and 512 include similar components as depicted forthe radar systems 302, 402, and 412 of FIGS. 3, 4-1, and 4-2,respectively. For example, the radar systems 502 and 512 include thetransmitters 304, receivers 306, a processor, CRM, polyphase shifters308, VCO 312, LNAs 314, mixers 316, BPFs 318, ADCs 320, and DSP 322. Thepolyphase shifters 308 are operatively coupled to the transmitters 304and VCO 312 in the transmit paths and the LNAs 314 and mixers 316 in thereceive path.

In FIG. 5-1, the polyphase shifters 308 are operatively coupled to eachreceive channel and then operatively coupled to a single down-conversionor analog-to-digital conversion channel in the receive path. In FIG.5-2, the polyphase shifters 308 are operatively coupled to each receivechannel and a subset of the receive channels or polyphase shifters 308are then operatively coupled to a down-conversion or analog-to-digitalconversion channel in the receive path. As illustrated in the conceptualdiagram 510, the radar system 512 includes two polyphase shifters 308 orreceive channels per down-conversion or analog-to-digital conversionchannel in the receive path. In other implementations, the radar system512 can include another number of polyphase shifters 308 or receivechannels per down-conversion or analog-to-digital conversion channel inthe receive path, resulting in N receive groups with M receive channelsper receive group in the receive path.

The polyphase shifters 308 can be operatively coupled to differentcomponents in the transmit paths and the receive paths in otherimplementations. In the radar systems 502 and 512, the polyphaseshifters 308 are respectively associated with both the transmitters 304and the receivers 306. The polyphase shifters 308 can apply or introducea phase shift to the transmitted EM signals and/or the received EMsignals in the depicted implementation.

As described above, each polyphase shifter 308 has multiple potentialoutput stages (e.g., 4, 8, 16, 32, or 64 stages). For example, theprocessor 118 can provide the polyphase control signal 310 to thepolyphase shifters 308 to control or set the phase stage of eachpolyphase shifter 308. The polyphase control signal 310 can be amultiple-bit signal (e.g., 2-bit, 3-bit, 4-bit, 5-bit, or 6-bit),allowing the polyphase shifters 308 to have more than two phase stages.The increased number of potential phase stages provides more flexibilityin a coding scheme applied by the radar system 502 or 512 to thetransmitted EM signals and/or received EM signals than binary phaseshifters can provide. The polyphase control signal 310 can add aprogressive phase modulation ϕ to the transmitted EM signal pulsesand/or the received EM signal pulses, which shifts the frequency orDoppler frequency of the reflected EM signals by an offset frequencyω_(c), which is equal to the produce of two, pi, and the phasemodulation (e.g., ω_(c)=2πϕ).

FIG. 6 illustrates an example diagram 600 of transmitted EM signalsusing FDM with polyphase shifters. For example, the diagram 600illustrates the EM signals transmitted by the transmitters 304 of FIG. 3or 5. In other implementations, the diagram 600 can illustrate the EMsignals received by the receivers 306 of FIG. 4 or 5. As describedabove, the transmitters 304 can transmit a linear frequency-modulatedsignal (e.g., chirping signal), phase-modulated continuous wave (PMCW)signal, or pulse signal (e.g., unmodulated signal) in otherimplementations.

The diagram 600 illustrates an example strategy for controlling thetransmitters 304 and/or the receivers 306. For example, a first one ofthe transmitters 304 transmits a first signal pulse 602 based onoperation of the VCO 312. The first signal pulse 602 has a first phase,which corresponds to zero degrees in this example. The first phase maybe considered a base or reference phase.

A second one of the transmitters 304 transmits a second signal pulse 604based on operation of the VCO 312 and the respective polyphase shifter308. The second signal pulse 604 has a second phase, which isphase-shifted from the first signal pulse 602 by a shift phase of ϕ. Asa result, the second phase is offset by a channel frequency cot, whichis equal to 2πϕ, from the first phase.

A third one of the transmitters 304 transmits a third signal pulse 606based on operation of the VCO 312 and the respective polyphase shifter308. The third signal pulse 606 has a third phase, which isphase-shifted from the first signal pulse 602 by a shift phase of 2ϕ. Asa result, the third phase is offset by a channel frequency 2ω_(c) fromthe first phase.

A fourth one of the transmitters 304 transmits a fourth signal pulse 608based on operation of the VCO 312 and the respective polyphase shifter308. The fourth signal pulse 608 has a fourth phase, which isphase-shifted from the first signal pulse 602 by a shift phase of 3ϕ. Asa result, the fourth phase is offset by a channel frequency 3ω_(c) fromthe first phase.

A fifth one of the transmitters 304 transmits a fifth signal pulse 610based on operation of the VCO 312 and the respective polyphase shifter308. The fifth signal pulse 610 has a fifth phase, which isphase-shifted from the first signal pulse 602 by a shift phase of 4ϕ. Asa result, the fifth phase is offset by a channel frequency 4ω_(c) fromthe first phase.

A sixth one of the transmitters 304 transmits a sixth signal pulse 612based on operation of the VCO 312 and the respective polyphase shifter308. The sixth signal pulse 612 has a sixth phase, which isphase-shifted from the first signal pulse 602 by a shift phase of 5ϕ. Asa result, the sixth phase is offset by a channel frequency 5ω_(c) fromthe first phase.

Having signal pulses transmitted simultaneously and including a phaseshift makes it possible to accurately recover the received EM signalinformation without Doppler ambiguity. The MIMO features can also reduceor eliminate signal-to-noise loss. In other implementations, the radarsystem can use a mixture of FDM and CM (e.g., code divisionmultiplexing) schemes to apply the described phase shifts to thetransmitted EM signals. The radar system can also use a pseudorandomouter code to apply the described phase shifts.

FIG. 7 illustrates an example graph 700 of a received EM signal of aradar system using FDM with polyphase shifters in a Doppler binrepresentation. The radar system can be the radar system 104 of FIGS. 1and 2, the radar system 302 of FIG. 3, the radar system 402 of FIG. 4-1,the radar system 412 of FIG. 4-2, the radar system 502 of FIG. 5-1, orthe radar system 512 of FIG. 5-2.

The received EM signal corresponds to one of the signal pulses andincludes a first peak 702. The first peak 702 has a first magnitude andis centered at the frequency-shifted signal 704, which is dependent onthe Doppler frequency ω_(D) 706 and the frequency shift ω_(c) 708. Asdescribed with respect to FIG. 6, the frequency shift 708 isproportional to the phase shift introduced by the polyphase shifters308. The Doppler frequency 706 is related to the relative difference invelocity between the object 110 and the radar system 104. In thedescribed radar system 104, the received EM signals can include severalpeaks associated with a single object 110. The techniques and systemsdescribed with respect to FIGS. 8 through 17 enable the radar system 104to identify the actual peaks associated with the object 110 and resolveDoppler ambiguities in the received EM signals.

Example Methods

FIG. 8 illustrates an example method 800 for a radar system that usesFDM with polyphase shifters to determine a Doppler frequency of objects.Method 800 is shown as sets of operations (or acts) performed, but notnecessarily limited to the order or combinations in which the operationsare shown herein. Further, any of one or more of the operations may berepeated, combined, or reorganized to provide other methods. In portionsof the following discussion, reference may be made to the environment100 of FIG. 1, and entities detailed in FIGS. 1 through 7, reference towhich is made for example only. The techniques are not limited toperformance by one entity or multiple entities. For example, the radarsystem can be the radar system 104 of FIGS. 1 and 2, the radar system302 of FIG. 3, the radar system 402 of FIG. 4-1, the radar system 412 ofFIG. 4-2, the radar system 502 of FIG. 5-1, or the radar system 512 ofFIG. 5-2 that determines a Doppler frequency of objects 110 surroundingthe vehicle 102.

At 802, the EM signals are transmitted by multiple transmitters of aradar system in an FDM scheme. The radar system including a first numberof transmitters. For example, the transmitters 304 can transmit EMsignals in an FDM scheme.

At 804, EM signals reflected by one or more objects are received bymultiple receivers of the radar system. The radar system including asecond number of receivers. The received EM signals include a number ofchannels equal to the product of the number of transmitters (e.g., thefirst number) and the number of receivers (e.g., the second number). Forexample, the receivers 306 can receive EM signals reflected by theobjects 110. The objects 110 can reflect the EM signals transmitted bythe transmitters 304. The received EM signals include a third number ofchannels, equal to the product of the first number and the secondnumber.

At 806, multiple polyphase shifters are controlled to introduce a phaseshift to the transmitted EM signals and/or the received EM signals. Themultiple polyphase shifters are operably connected to the multipletransmitters and/or the multiple receivers of the radar system. Thephase shift includes one of at least three potential phase shifts. Forexample, the polyphase shifters 308 are operably connected to thetransmitters 304 and/or the receivers 306. The processor 118 can controlthe polyphase shifters 308 to introduce a phase shift to the transmittedEM signals and/or the received EM signals, wherein the phase shiftincludes one of at least three potential phase shifts. As describedabove, the processor 118 can use the polyphase control signal 310 tocontrol the phase shifters 308. The polyphase control signal 310 can bea multiple-bit signal (e.g., 2-bit, 3-bit, 4-bit, 5-bit, or 6-bit),allowing the polyphase shifters 308 to have more than two phase stages.The increased number of potential phase stages provides more flexibilityin a coding scheme applied to the transmitted EM signals and/or receivedEM signals than binary phase shifters can provide.

At 808, a Doppler-frequency spectrum of the received EM signals isdivided into a fourth number of sectors. The sectors represent arespective frequency range within the Doppler-frequency spectrum. Thenumber of sectors can be equal to or greater than the number of channels(e.g., the third number). For example, the spectrum analysis module 122can divide the Doppler-frequency spectrum of the received EM signalsinto sectors. The number and size of the sectors can be selected toavoid a symmetrical radiation pattern among the channels in the receivedEM signals, as described in greater detail with respect to FIGS. 9through 11.

At 810, each channel of the received EM signals is associated to arespective sector of the sectors. For example, the spectrum analysismodule 122 can associate the channels of the received EM signals to arespective sector of the sectors. The association of the channels torespective sectors is described in greater detail with respect to FIGS.9 through 11.

At 812, non-coherent integration is performed on the received EM signalsacross the sectors using at least one channel of the received EMsignals. For example, the non-coherent integrator 124 can performnon-coherent integration on the received EM signals across the sectorsof the Doppler-frequency spectrum. The non-coherent integration of thereceived EM signals is described in greater detail with respect to FIGS.12 through 17.

At 814, potential detections of the one or more objects are determinedbased on the non-coherent integration. The potential detections includeone or more actual detections and one or more aliased detections of theone or more objects. For example, the non-coherent integrator 124, theDSP 322, or the processor 118 can determine, based on the non-coherentintegration, potential detections of the objects 110. The identificationof potential detections for the objects 110 is described in greaterdetail with respect to FIGS. 12 through 17.

At 816, actual detections of the one or more objects are determinedbased on the potential detections. For example, the non-coherentintegrator 124, the DSP 322, or the processor 118 can determine, basedon the potential detections, the actual detections of the objects 110.The identification of actual detections for the objects 110 is describedin greater detail with respect to FIGS. 12 through 17.

At 818, a Doppler frequency associated with each of the one or moreobjects is determined based on the actual detections. For example, theDSP 322 or the processor 118 can determine, based on the actualdetections, the Doppler frequency associated with the objects 110. Theidentification of potential detections for the objects 110 is describedin greater detail with respect to FIGS. 12 through 17.

FIG. 9 illustrates an example graphical representation 900 of theassociation of channels and sectors in a radar system using FDM withpolyphase shifters. For example, the radar system can be the radarsystem 104 of FIGS. 1 and 2, the radar system 302 of FIG. 3, the radarsystem 402 of FIG. 4-1, the radar system 412 of FIG. 4-2, the radarsystem 502 of FIG. 5-1, or the radar system 512 of FIG. 5-2.

The graphical representation 900 illustrates energy of received EMsignals as a y-axis and a corresponding Doppler frequency of thereceived EM signals as an x-axis. The received EM signals include Nchannels 902, which are represented in FIG. 9 by the triangular peakscorresponding to an actual detection or aliased detection within eachchannel.

The radar system 104 or the spectrum analysis module 122 divides theDoppler-frequency spectrum of the received EM signals into M sectors904, which are equally sized. The sectors 904 represent a range offrequencies within the Doppler-frequency spectrum for the received EMsignals. The radar system 104 or the spectrum analysis module 122selects the number M of sectors 904 to be at least one greater than thenumber N of channels 902 (e.g., M≥N+erally, the number M of sectors 904is maintained sufficiently small to maintain separation among thechannels 902 within the Doppler-frequency spectrum. Consider that theDoppler-frequency spectrum is divided into six sectors 904 (e.g., Mequals six), and the spectrum analysis module 122 can assign each sectora frequency range of π/3 sixty degrees.

The radar system 104 or the spectrum analysis module 122 associates orplaces the channels 902 in separate sectors, with one channel 902 persector 904. Because the number N of channels 902 is less than the numberM of sectors 904, there are one or more empty sectors 906 without acorresponding channel. The empty sectors 906 can be placed in variouslocations within the Doppler-frequency spectrum, including among,before, or after the channels 902. The placement of the channels 902 andthe empty sectors 906 are arranged to avoid forming a symmetricalspectrum that can lead to ambiguity in resolving detections of theobjects 110.

Placement of the channels 902 among the sectors 904 affects thenon-coherent integration and de-aliasing logic used by the radar system104 and/or the non-coherent integrator 124. For example, the radarsystem 104 or the non-coherent integrator 124 can perform non-coherentintegration over a combination of N sectors 904 (e.g., C_(N+M) ^(N)) toform (N+M) spectrums. The radar system 104 can then form a finalnon-coherent integrated spectrum by taking a maximum over the (N+M)spectrums at each frequency bin. The radar system 104 can then find thesector corresponding to each object from the combination that has themaximum value.

As another example, the radar system 104 or the spectrum analysis module122 can divide the Doppler spectrum into 2^(M) equal sectors 904, wherethe number N of channels is less than 2^(M) but greater than or equal to2^(M−1) (e.g., 2^(M−1)≤N<2^(M)). The radar system 104 associates orplaces the channels 902 in separate sectors, with one channel 902 persector 904 and (2^(M)−N) empty sectors 906. The empty sectors 906 can beplaced in various locations within the Doppler spectrum, includingamong, before, or after the channels 902. If the number N of channels902 is even, the channels 902 are asymmetrically placed among thesectors 904. The radar system 104 can perform non-coherent integrationover consecutive N sectors 904 (e.g., C_(N+M) ^(N)) to form 2^(M)spectrums. As described in greater detail with respect to FIGS. 15 and16, the radar system 104 can then form a final non-coherent integratedspectrum by taking a maximum over the 2^(M) spectrums at each frequencybin. The radar system 104 can then find the sector corresponding to eachobject from the combination that has the maximum value.

FIG. 10 illustrates an example graphical representation 1000 of theassociation of channels and sectors in a radar system using FDM withpolyphase shifters. For example, the radar system can be the radarsystem 104 of FIGS. 1 and 2, the radar system 302 of FIG. 3, the radarsystem 402 of FIG. 4-1, the radar system 412 of FIG. 4-2, the radarsystem 502 of FIG. 5-1, or the radar system 512 of FIG. 5-2.

The graphical representation 1000 illustrates energy of received EMsignals as a y-axis and a corresponding Doppler frequency of thereceived EM signals as an x-axis. The received EM signals include Nchannels 1002, which are represented in FIG. 10 by the triangular peakscorresponding to an actual detection or aliased detection within eachchannel.

The radar system 104 or the spectrum analysis module 122 divides thereceived EM signals into M sectors 1004, which have a non-uniform size1006. The sectors 1004 represent a range of frequencies within theDoppler-frequency spectrum for the received EM signals. The radar system104 or the spectrum analysis module 122 selects the number M of sectors1004 to be equal to the number N of channels 1002 (e.g., M=N). Considerthat the Doppler spectrum is divided into six sectors 1004 (e.g.,Mequals six), each sector 1004 will have a corresponding size 1006 thatis different for each sector 1004 (e.g., D₁≠D₂≠D₃≠D₄≠D₅≠D₆). The radarsystem 104 or the spectrum analysis module 122 associates or places thechannels 1002 in separate sectors 1004, with one channel 1002 per sector1004. Because each sector 1004 has a different size 1006, the channels1002 are asymmetrical and Doppler ambiguity in resolving detections ofthe obj ects 110 is avoided.

FIG. 11 illustrates an example graphical representation 1100 of theassociation of channels and sectors in a radar system using FDM withpolyphase shifters. For example, the radar system can be the radarsystem 104 of FIGS. 1 and 2, the radar system 302 of FIG. 3, the radarsystem 402 of FIG. 4-1, the radar system 412 of FIG. 4-2, the radarsystem 502 of FIG. 5-1, or the radar system 512 of FIG. 5-2.

The graphical representation 1100 illustrates energy of received EMsignals as a y-axis and a corresponding Doppler frequency of thereceived EM signals as an x-axis. The EM signals include N channels1102, which are represented in FIG. 11 by the triangular peakscorresponding to an actual detection or aliased detection within eachchannel.

The radar system 104 or spectrum analysis module 122 divides thereceived EM signals into M sectors 1104, which have a combination ofuniform and non-uniform sizes or spacing 1106. In other words, somesubset of sectors 1104 have a uniform size 1106 and one or more othersubsets of 1104 have a different size 1106. The sectors 1104 represent arange of frequencies within the Doppler-frequency spectrum for the EMsignals. The radar system 104 or the spectrum analysis module 122selects the number M of sectors 1104 to be equal to the number N ofchannels 1102 (e.g., M=N). Consider that the Doppler spectrum is dividedinto six sectors 1104 (e.g., M equals six), sectors 1104-1 and 1104-2can have a first spacing D₁ 1106-1, sector 1104-3 can have a secondspacing D₂ 1106-2, and sectors 1104-4, 1104-5, and 1104-6 can have athird spacing D₃ 1106-3. The radar system 104 or the spectrum analysismodule 122 associates or places the channels 1102 in separate sectors,with one channel 1102 per sector 1104. Because of the combination ofuniform and non-uniform sizes 1006, the channels 1002 are asymmetricaland Doppler ambiguity in resolving detections of the objects 110 isavoided.

FIG. 12 illustrates an example flowchart 1200 for a radar system thatuses FDM with polyphase shifters to perform non-coherent integration anddetermine actual detections associated with objects. For example, theradar system can be the radar system 104 of FIGS. 1 and 2, the radarsystem 302 of FIG. 3, the radar system 402 of FIG. 4-1, the radar system412 of FIG. 4-2, the radar system 502 of FIG. 5-1, or the radar system512 of FIG. 5-2 that determines actual detections for the objects 110surrounding the vehicle 102.

At 1202, the radar system 104 receives EM energy. For example, thereceivers 114 of the radar system 104 can receive EM energy reflected bythe objects 110. The objects 110 can reflect EM energy transmitted bythe transmitters 112. The radar system 104 also divides the Dopplerfrequencies of the received EM energy into sectors and associates thechannels with the sectors, as described in greater detail with respectto FIGS. 8 through 11. Graphical plot 1210 illustrates the potentialdetections 1212, 1214, and 1216 in a three-channel radar system. Thegraphical plot 1210 illustrates the energy associated with the potentialdetections 1212, 1214, and 1216 versus the corresponding Dopplerfrequency.

At 1204, the radar system 104 generates a first logical list ofpotential detections for a first channel of the channels using aconstant false alarm rate (CFAR) threshold. The CFAR threshold is usedto detect object reflections against a background of noise, clutter, andinterference in the received EM signals for the single channel. In thisapproach, the CFAR threshold can be reduced or smaller than a typicalCFAR threshold value because a single channel of the channels is beinganalyzed. For example, the radar system 104 can use a reduced CFAR toaccount for the gain difference in the received EM signal for a singlechannel compared to the non-coherent integrated gain from multiplechannels.

The first logical list indicates the potential detections withinrespective Doppler bins that include a peak with EM energy greater thanthe CFAR threshold. In other words, a logical detection (e.g., thelogical detections 1220, 1222, and 1224) is identified by any energypeaks in the received EM signal that are larger than the reduced CFARthreshold. The logical list represents Doppler bins within theDoppler-frequency spectrum. The logical detection list 1218 illustratesa logical detection 1220 in a Doppler bin that corresponds to the centerDoppler frequency of the potential detection 1212. Similarly, logicaldetection 1222 and 1224 correspond to the center Doppler frequencies ofthe potential detections 1214 and 1216, respectively.

At 1206, the radar system 104 or the non-coherent integrator 124performs, based on the sectors, one or more circular shifts on the firstlogical list of potential detections to generate additional logicallists. The number of circular shifts is equal to the number N ofchannels minus one (e.g., N−1). In the depicted implementation, twocircular shifts are performed on the logical detection list 1218,resulting in logical detections lists 1226 and 1234. The logicaldetection list 1226 includes logical detections 1228, 1230, and 1232.The logical detection list 1234 includes logical detections 1236, 1238,and 1240.

At 1208, the radar system 104 or the non-coherent integrator 124determines or generates a final detection list of actual detectionsusing a logical AND operator over the logical lists. For example, theradar system 104 or the non-coherent integrator 124 determines theactual detections of the objects 110 by performing a logical ANDoperation on the logical lists 1218, 1226, and 1234 at each Doppler binof the logical lists. As illustrated in the final detection list 1242,an actual detection 1244 is identified at a particular Doppler bin,which corresponds to the logical detections 1224, 1232, and 1240. Byusing a single channel and circular shifts thereof, the radar system 104can process the radar data faster.

FIG. 13 illustrates another example flowchart 1300 for a radar systemthat uses FDM with polyphase shifters to perform non-coherentintegration and determine actual detections associated with objects. Forexample, the radar system can be the radar system 104 of FIGS. 1 and 2,the radar system 302 of FIG. 3, the radar system 402 of FIG. 4-1, theradar system 412 of FIG. 4-2, the radar system 502 of FIG. 5-1, or theradar system 512 of FIG. 5-2 that determines actual detections for theobjects 110 surrounding the vehicle 102.

At 1302, the radar system 104 receives EM energy. For example, thereceivers 114 of the radar system 104 can receive EM energy reflected bythe objects 110. The objects 110 can reflect EM energy transmitted bythe transmitters 112. The radar system 104 can generate a first EMspectrum of the received EM signals for a first channel of the channels.The radar system 104 also divides the Doppler frequencies of thereceived EM energy into sectors and associates the channels with thesectors as described in greater detail with respect to FIGS. 8 through11. Graphical plot 1308 illustrates the potential detections 1310, 1312,and 1314 in a three-channel radar system. The graphical plot 1308illustrates the energy associated with the potential detections 1310,1312, and 1314 versus the corresponding Doppler frequency.

At 1304, the radar system 104 performs, based on the sectors, one ormore circular shifts on the first EM spectrum to generate additional EMspectrums of the received EM signals. The number of circular shifts isequal to the number N of channels minus one (e.g., N−1). In the depictedimplementation, two circular shifts are performed on the graphical plot1308, resulting in graphical plots 1316 and 1318. The graphical plots1316 and 1318 illustrate the potential detections 1310, 1312, and 1314at different center Doppler frequencies after the corresponding circularshift. For example, the graphical plot 1316 illustrates a circular shiftof the graphical plot 1308, and the graphical plot 1318 illustrates acircular shift of the graphical plot 1316.

At 1306, the radar system 104 determines, across the first andadditional EM spectrums, a sum of EM energy levels at each Doppler binof the EM spectrum. For example, the radar system 104 can sum across thegraphical plots 1308, 1316, and 1318 at each Doppler bin to generate thegraphical plot 1320. The graphical plot 1320 includes potentialdetections 1322, 1328, 1330, 1332, 1334, and 1336. The potentialdetection 1322 includes the sum of the EM energy associated with thepotential detections 1310, 1312, and 1314. In this way, the actuallocation of the object 110 within the Doppler-frequency spectrum getsfull integration, resulting in a higher gain for the potential detection1322. The aliased locations (e.g., the potential detections 1328-1338)have a relatively smaller gain.

At 1308, the radar system 104 generates a logical list 1340 (e.g., alogical detection list) of potential detections using a CFAR threshold.The CFAR threshold is used to detect object reflections against abackground of noise, clutter, and interference in the received EMsignals for the single channel. The logical list 1340 indicates thepotential detections within respective Doppler bins that include a peakwith EM energy greater than the CFAR threshold. In other words, alogical detection (e.g., the logical detections 1342, 1344, 1346, 1348,1350, 1352, and 1354) is identified by any energy peaks in the receivedEM signal that are larger than the reduced CFAR threshold. The logicallist represents Doppler bins within the Doppler-frequency spectrum. Thelogical detection list 1340 illustrates a logical detection in a Dopplerbin that corresponds to the center Doppler frequency of each potentialdetection.

At 1310, the radar system 104 determines the actual detections of theobjects 110 by identifying the aliased detects based on the associationof each of the channels of received EM signals to the respective sector.For example, the radar system 104 identifies the actual detection 1358in the final detection list 1356. The radar system 104 can recursivelyselect a potential detection from the preliminary detections as theactual final detection and identify potential aliased locations based onthe channel placement. The recursive process is continued until a finaldetection is selected that identifies the appropriate number of aliaseddetections. By using a summation of circular shifts of thesingle-channel data, the radar system 104 generates a higher gain foractual detections, making it easier to identify actual detections amongnoise, weak signals, and aliased detections.

FIG. 14 illustrates another example flowchart 1400 for a radar systemthat uses FDM with polyphase shifters to perform non-coherentintegration and determine actual detections associated with objects. Forexample, the radar system can be the radar system 104 of FIGS. 1 and 2,the radar system 302 of FIG. 3, the radar system 402 of FIG. 4-1, theradar system 412 of FIG. 4-2, the radar system 502 of FIG. 5-1, or theradar system 512 of FIG. 5-2 that determines a Doppler velocity ofobjects 110 surrounding the vehicle 102.

At 1402, the radar system 104 receives EM energy. For example, thereceivers 114 of the radar system 104 can receive EM energy reflected bythe objects 110. The objects 110 can reflect EM energy transmitted bythe transmitters 112. The radar system 104 can generate a first EMspectrum of the received EM signals for a first channel of the channels.The radar system 104 also divides the Doppler frequencies of thereceived EM energy into sectors and associates the channels with thesectors as described in greater detail with respect to FIGS. 8 through11. Graphical plot 1410 illustrates the potential detections 1412, 1414,and 1416 in a three-channel radar system of a single channel. Thegraphical plot 1410 illustrates the energy associated with the potentialdetections 1412, 1414, and 1416 versus the corresponding Dopplerfrequency.

At 1404, the radar system 104 performs, based on the sectors, one ormore circular shifts on the first EM spectrum to generate additional EMspectrums of the received EM signals. The number of circular shifts isequal to the number N of channels minus one (e.g., N−1). In the depictedimplementation, two circular shifts are performed on the graphical plot1410, resulting in graphical plots 1418 and 1420. The graphical plots1418 and 1420 illustrate the potential detections 1412, 1414, and 1416at different center Doppler frequencies after the corresponding circularshift. For example, the graphical plot 1418 illustrates a circular shiftof the graphical plot 1410 and the graphical plot 1420 illustrates acircular shift of the graphical plot 1418.

At 1406, the radar system 104 determines, across the first andadditional EM spectrums, a minimum EM energy level at each Doppler binof the EM spectrum. For example, the radar system 104 can take a minimumacross the graphical plots 1410, 1418, and 1420 at each Doppler bin togenerate graphical plot 1422. The graphical plot 1422 includes apotential detection 1424. In this way, the actual location of the object110 within the Doppler spectrum is identified because the aliaseddetections do not appear in each graphical plot at the same Doppler binacross each graphical plot.

At 1408, the radar system 104 generates a final detection list 1426(e.g., a logical detection list) and determines the actual detections ofthe objects 110. The actual detections are determined by determiningwhether the minimum EM energy level at a respective Doppler bin isgreater than a CFAR threshold. The final detection list 1426 indicatesin which Doppler bins an actual detection was identified. An actualdetection (e.g., the actual detection 1428) is identified by any energypeaks in the graphical plot 1422 that is larger than the CFAR threshold.The final detection list 1426 illustrates a logical detection in aDoppler bin that corresponds to the center Doppler frequency of eachpotential detection.

FIG. 15 illustrates another example flowchart 1500 for a radar systemthat uses FDM with polyphase shifters to perform non-coherentintegration and determine actual detections associated with objects. Forexample, the radar system can be the radar system 104 of FIGS. 1 and 2,the radar system 302 of FIG. 3, the radar system 402 of FIG. 4-1, theradar system 412 of FIG. 4-2, the radar system 502 of FIG. 5-1, or theradar system 512 of FIG. 5-2 that determines a Doppler velocity ofobjects 110 surrounding the vehicle 102.

At 1502, the radar system 104 receives EM energy. For example, thereceivers 114 of the radar system 104 can receive EM energy reflected bythe objects 110. The objects 110 can reflect EM energy transmitted bythe transmitters 112. The radar system 104 can generate a first EMspectrum of the received EM signals for a first channel of the channels.The radar system 104 also divides the Doppler frequencies of thereceived EM energy into equally-sized sectors and associates thechannels with the sectors as described in greater detail with respect toFIG. 9. Graphical plot 1510 illustrates the potential detections 1520,1522, and 1524 in a three-channel radar system of a single channel. Thegraphical plot 1510 illustrates the energy associated with the potentialdetections 1520, 1522, and 1524 versus the corresponding Dopplerfrequency.

At 1504, the radar system 104 or the non-coherent integrator 124determines, using the first EM spectrum and for each sector, asector-based integration of the EM energy. The radar system 104 or thenon-coherent integrator 124 can perform sector-based integration orsummation on the EM energy received by the single channel. The number ofsectors integrated together is equal to the number N of channels minusone (e.g., N−1). The number of sector-based integrations is equal to thenumber N of channels. In the depicted implementation, each sector-basedintegration includes three consecutive sectors. For example, for apotential target in the sector 1512, the radar system 104 integrates theEM energy in the sectors 1512, 1514, and 1516 together. For a potentialtarget in the sector 1514, the radar system 104 integrates the EM energyin the sectors 1514, 1516, and 1518. For a potential target in thesector 1516, the radar system 104 integrates the EM energy in thesectors 1516, 1518, and 1512. And for a potential target in the sector1518, the radar system 104 integrates the EM energy in the sectors 1518,1512, and 1514.

Graphical plot 1526 illustrates the result of the sector-basedintegration, which includes potential detections 1528, 1530, 1532, and1534. In this way, the actual location of the object 110 within theDoppler spectrum gets a larger integration, resulting in a higher gainfor the corresponding potential detection 1528. The aliased locations(e.g., the potential detections 1530, 1532, and 1534) have a relativelysmaller gain.

At 1506, the radar system 104 or non-coherent integrator 124 determinesa maximum EM energy level for the sector-based integration of the EMenergy. For example, the radar system 104 can take a maximum across thegraphical plot 1526 to generate the graphical plot 1536. The graphicalplot 1536 includes the potential detection 1528. In this way, the actuallocation of the object 110 within the Doppler-frequency spectrum isidentified because the aliased detections do not obtain the sameintegrated gain as the actual detection.

At 1508, the radar system 104 generates a final detection list 1538(e.g., a logical detection list) using a CFAR threshold to determine theactual detections. The final detection list 1538 indicates in whichDoppler bin an actual detection was identified. An actual detection(e.g., the actual detection 1540) is identified by any energy peaks inthe graphical plot 1536 that are larger than the CFAR threshold. Thefinal detection list 1538 illustrates a logical detection in a Dopplerbin that corresponds to the center Doppler frequency of each potentialdetection.

FIG. 16 illustrates another example flowchart 1600 for a radar systemthat uses FDM with polyphase shifters to perform non-coherentintegration and determine actual detections associated with objects. Forexample, the radar system can be the radar system 104 of FIGS. 1 and 2,the radar system 302 of FIG. 3, the radar system 402 of FIG. 4-1, theradar system 412 of FIG. 4-2, the radar system 502 of FIG. 5-1, or theradar system 512 of FIG. 5-2 that determines a Doppler velocity ofobjects 110 surrounding the vehicle 102.

At 1602, the radar system 104 receives EM energy. For example, thereceivers 114 of the radar system 104 can receive EM energy reflected bythe objects 110. The objects 110 can reflect EM energy transmitted bythe transmitters 112. The radar system 104 can generate a first EMspectrum of the received EM signals for a first channel of the channels.The radar system 104 also divides the Doppler frequencies of thereceived EM energy into equally-sized sectors and associates thechannels with the sectors as described in greater detail with respect toFIG. 9. Graphical plot 1612 illustrates the potential detections 1614,1616, and 1618 in a three-channel radar system of a single channel. Thegraphical plot 1612 illustrates the energy associated with the potentialdetections 1614, 1616, and 1618 versus the corresponding Dopplerfrequency.

At 1604, the radar system 104 or the non-coherent integrator 124performs, based on the sectors, one or more circular shifts on the firstEM spectrum to generate additional EM spectrums of the received EMsignals. The number of circular shifts is equal to the number N ofchannels minus one (e.g., N−1). In the depicted implementation, twocircular shifts are performed on the graphical plot 1612, resulting ingraphical plots 1620 and 1622. The graphical plots 1620 and 1622illustrate the potential detections 1614, 1616, and 1618 at differentcenter Doppler frequencies after the corresponding circular shift. Forexample, the graphical plot 1620 illustrates a circular shift of thegraphical plot 1612 and the graphical plot 1622 illustrates a circularshift of the graphical plot 1620.

At 1606, the radar system 104 or the non-coherent integrator 124determines, using the first and additional EM spectrums and for eachsector, a sector-based integration of EM energy. The sector-basedintegration represents a sum of the EM energy of the respective sectoracross the first and additional EM spectrums. For example, the radarsystem 104 can sum across the graphical plots 1612, 1620, and 1622 ateach Doppler bin to generate the graphical plot 1624. The graphical plot1624 includes potential detections 1626, 1628, 1630, and 1632. Thepotential detection 1626 includes the sum of the EM energy associatedwith the potential detections 1614, 1616, and 1618. In this way, theactual location of the object 110 within the Doppler spectrum gets fullintegration, resulting in a higher gain for the potential detection1626. The aliased locations (e.g., the potential detections 1628, 1630,and 1632) have a relatively smaller gain.

At 1608, the radar system 104 or the non-coherent integrator 124determines a maximum EM energy level for the sector-based integration ofEM energy. For example, the radar system 104 can take the maximum acrossthe graphical plot 1624 to generate the graphical plot 1634. Thegraphical plot 1634 includes the potential detection 1626. In this way,the actual location of the object 110 within the Doppler-frequencyspectrum is identified because the aliased detections result in a lowersummed gain.

At 1610, the radar system 104 generates a final detection list 1636(e.g., a logical detection list) of the actual detections. The finaldetection list 1636 indicates in which Doppler bins an actual detection1638 was identified. The final detection list 1636 illustrates a logicaldetection in a Doppler bin that corresponds to the center Dopplerfrequency of the actual detection 1638.

FIG. 17 illustrates another example flowchart 1700 for a radar systemthat uses FDM with polyphase shifters to perform non-coherentintegration and determine actual detections associated with objects. Forexample, the radar system can be the radar system 104 of FIGS. 1 and 2,the radar system 302 of FIG. 3, the radar system 402 of FIG. 4-1, theradar system 412 of FIG. 4-2, the radar system 502 of FIG. 5-1, or theradar system 512 of FIG. 5-2 that determines a Doppler velocity ofobjects 110 surrounding the vehicle 102. The flowchart 1700 includes thesame four operations (e.g., the operations 1602, 1604, 1606, and 1608)as the flowchart 1600.

At 1602, the radar system 104 receives EM energy. For example, thereceivers 114 of the radar system 104 can receive EM energy reflected bythe objects 110. The objects 110 can reflect EM energy transmitted bythe transmitters 112. The radar system 104 can generate a first EMspectrum of the received EM signals for a first channel of the channels.The radar system 104 also divides the Doppler frequencies of thereceived EM energy into equally-sized sectors and associates thechannels with the sectors as described in greater detail with respect toFIG. 9. Graphical plot 1612 illustrates the potential detections 1614,1616, and 1618 in a three-channel radar system of a single channel. Thegraphical plot 1612 illustrates the energy associated with the potentialdetections 1614, 1616, and 1618 versus the corresponding Dopplerfrequency.

At 1604, the radar system 104 or the non-coherent integrator 124performs, based on the sectors, one or more circular shifts on the firstEM spectrum to generate additional EM spectrums of the received EMsignals. The number of circular shifts is equal to the number N ofchannels minus one (e.g., N−1). In the depicted implementation, twocircular shifts are performed on the graphical plot 1612, resulting ingraphical plots 1620 and 1622. The graphical plots 1620 and 1622illustrate the potential detections 1614, 1616, and 1618 at differentcenter Doppler frequencies after the corresponding circular shift. Forexample, the graphical plot 1620 illustrates a circular shift of thegraphical plot 1612 and the graphical plot 1622 illustrates a circularshift of the graphical plot 1620.

At 1606, the radar system 104 or the non-coherent integrator 124determines, using the first and additional EM spectrums and for eachsector, a sector-based integration of EM energy. The sector-basedintegration represents a sum of the EM energy of the respective sectoracross the first and additional EM spectrums. For example, the radarsystem 104 can sum across the graphical plots 1612, 1620, and 1622 ateach Doppler bin to generate the graphical plot 1624. The graphical plot1624 includes potential detections 1626, 1628, 1630, and 1632. Thepotential detection 1626 includes the sum of the EM energy associatedwith the potential detections 1614, 1616, and 1618. In this way, theactual location of the object 110 within the Doppler spectrum gets fullintegration, resulting in a higher gain for the potential detection1626. The aliased locations (e.g., the potential detections 1628, 1630,and 1632) have a relatively smaller gain.

At 1608, the radar system 104 or the non-coherent integrator 124determines a maximum EM energy level for the sector-based integration ofEM energy. For example, the radar system 104 can take the maximum acrossthe graphical plot 1624 to generate the graphical plot 1634. Thegraphical plot 1634 includes the potential detection 1626. In this way,the actual location of the object 110 within the Doppler-frequencyspectrum is identified because the aliased detections result in a lowersummed gain.

At 1702, the radar system 104 or the non-coherent integrator 124determines a minimum EM energy level at each Doppler bin of the EMspectrum. For example, the radar system 104 or the non-coherentintegrator 124 can take a minimum across the graphical plots 1612, 1620,and 1622 at each Doppler bin to generate the graphical plot 1708. Thegraphical plot 1708 includes a potential detection 1710. In this way,the actual location of the object 110 within the Doppler spectrum isidentified because the aliased detections do not appear in eachgraphical plot at the same Doppler bin across each graphical plot.

At 1704, the radar system 104 or the non-coherent integrator 124generates a preliminary minimum detection list 1712 and a preliminarymaximum detection list 1716 using a CFAR threshold. The preliminaryminimum detection list 1712 includes a potential detection 1714. Thepreliminary maximum detection list 1716 includes a potential detection1718. The CFAR threshold is used to detect object reflections against abackground of noise, clutter, and interference in the received EMsignals for the single channel. The preliminary minimum detection list1712 indicates the potential detections within respective Doppler binsfor the graphical plot 1708 that include a peak with EM energy greaterthan the CFAR threshold. The preliminary maximum detection list 1716indicates the potential detections within respective Doppler bins forthe graphical plot 1708 that include a peak with EM energy greater thanthe CFAR threshold.

At 1706, the radar system 104 generates a final detection list 1720 ofactual detections using a logical AND operator on the preliminaryminimum detection list 1712 and the preliminary maximum detection list1716 at each Doppler bin. The final detection list 1720 indicates inwhich Doppler bins an actual detection 1722 was identified. The finaldetection list 1720 illustrates a logical detection in a Doppler binthat corresponds to the center Doppler frequency of the actual detection1722.

EXAMPLES

In the following section, examples are provided.

Example 1

A radar system comprising: multiple transmitters configured to transmitelectromagnetic (EM) signals in a frequency-division multiplexing (FDM)scheme; multiple receivers configured to receive EM signals reflected byone or more objects; multiple polyphase shifters operably connected tothe multiple transmitters, the multiple receivers, or a combinationthereof, the multiple polyphase shifters configured to introduce atleast three potential phase shifts; and a processor configured tocontrol the multiple polyphase shifters to introduce a phase shift to atleast one of the transmitted EM signals or the received EM signals.

Example 2

The radar system of example 1, wherein: the multiple transmitterscomprise a first number of transmitters; the multiple receivers comprisea second number of receivers, the second number being equal or not equalto the first number; the multiple polyphase shifters comprise a thirdnumber of polyphase shifters, the third number being equal to the firstnumber, the second number, or a sum of the first number and the secondnumber; and the received EM signals comprise a fourth number ofchannels, the fourth number being equal to a product of the first numberand the second number.

Example 3

The radar system of example 2, wherein: the multiple polyphase shiftersare operably connected to the multiple transmitters; and the thirdnumber is equal to the first number.

Example 4

The radar system of example 2, wherein: the multiple polyphase shiftersare operably connected to the multiple receivers; and the third numberis equal to the second number.

Example 5

The radar system of example 2, wherein: the multiple polyphase shiftersare operably connected to the multiple transmitters and the multiplereceivers; and the third number is equal to the sum of the first numberand the second number.

Example 6

The radar system of example 2, wherein the processor is furtherconfigured to: divide a Doppler-frequency spectrum of the received EMsignals into a fifth number of sectors, the sectors representing arespective frequency range within the Doppler-frequency spectrum andbeing equally sized within the Doppler-frequency spectrum, the fifthnumber being equal to or greater than the fourth number plus one; andassociate each of the channels of the received EM signals to arespective sector of the sectors, at least one of the sectors not beingassociated with a channel of the received EM signals, the association ofthe channels to the sectors being configured to form an asymmetricalspectrum.

Example 7

The radar system of example 2, wherein the processor is furtherconfigured to: divide a Doppler-frequency spectrum of the received EMsignals into the fourth number of sectors, the sectors representing arespective frequency range within the Doppler-frequency spectrum andbeing unequally sized within the Doppler-frequency spectrum; andassociate each of the channels of the received EM signals to arespective sector of the sectors, the association of the channels to theunequal sectors being configured to form an asymmetrical spectrum.

Example 8

The radar system of example 2, wherein the processor is furtherconfigured to: divide a Doppler-frequency spectrum of the received EMsignals into the fourth number of sectors, the sectors representing arespective frequency range within the Doppler-frequency spectrum, asubset of the sectors being equally sized within the Doppler-frequencyspectrum and another subset of the sectors being unequally sized withinthe Doppler-frequency spectrum; and associate each of the channels ofthe received EM signals to a respective sector of the sectors, theassociation of the channels to the sectors being configured to form anasymmetrical spectrum.

Example 9

The radar system of any preceding example, wherein the processor isfurther configured to control the multiple polyphase shifters todynamically adjust the phase shift introduced to at least one of thetransmitted EM signals or the received EM signals.

Example 10

The radar system of any preceding example, wherein the multipletransmitters and the multiple receivers are configured to operate aspart of a multiple-input and multiple-output (MIMO) radar approach.

Example 11

The radar system of any preceding example, wherein the radar system isconfigured to be installed on an automobile.

Example 12

A computer-readable storage media comprising computer-executableinstructions that, when executed, cause a processor of a radar systemto: transmit, via multiple transmitters of the radar system,electromagnetic (EM) signals in a frequency-division multiplexing (FDM)scheme; receive, via multiple receivers of the radar system, EM signalsreflected by one or more objects; and control multiple polyphaseshifters to introduce a phase shift to at least one of the transmittedEM signals or the received EM signals, the multiple polyphase shiftersbeing operably connected to the multiple transmitters, the multiplereceivers, or a combination thereof, the introduced phase shiftcomprising one of at least three potential phase shifts.

Example 13

The computer-readable storage media of example 12, wherein: the multipletransmitters comprise a first number of transmitters; the multiplereceivers comprise a second number of receivers, the second number beingequal or not equal to the first number; the multiple polyphase shifterscomprise a third number of polyphase shifters, the third number beingequal to the first number, the second number, or a sum of the firstnumber and the second number; and the received EM signals comprise afourth number of channels.

Example 14

The computer-readable storage media of example 13, wherein: the multiplepolyphase shifters are operably connected to the multiple transmitters;and the third number is equal to the first number.

Example 15

The computer-readable storage media of example 13, wherein: the multiplepolyphase shifters are operably connected to the multiple receivers; andthe third number is equal to the second number.

Example 16

The computer-readable storage media of example 13, wherein: the multiplepolyphase shifters are operably connected to the multiple transmittersand the multiple receivers; and the third number is equal to the sum ofthe first number and the second number.

Example 17

The computer-readable storage media of example 13, wherein theinstructions, when executed, further cause the processor of the radarsystem to: divide a Doppler-frequency spectrum of the received EMsignals into a fifth number of sectors, the sectors representing arespective frequency range within the Doppler-frequency spectrum andbeing equally sized within the Doppler-frequency spectrum, the fifthnumber being equal to or greater than the fourth number plus one; andassociate each of the channels of the received EM signals to arespective sector of the sectors, at least one of the sectors not beingassociated with a channel of the received EM signals, the association ofthe channels to the sectors being configured to form an asymmetricalspectrum.

Example 18

The computer-readable storage media of example 13, wherein theinstructions, when executed, further cause the processor of the radarsystem to: divide a Doppler-frequency spectrum of the received EMsignals into the fourth number of sectors, the sectors representing arespective frequency range within the Doppler-frequency spectrum andbeing unequally sized within the Doppler-frequency spectrum; andassociate each of the channels of the received EM signals to arespective sector of the sectors, the association of the channels to theunequal sectors being configured to form an asymmetrical spectrum.

Example 19

The computer-readable storage media of example 13, wherein theinstructions, when executed, further cause the processor of the radarsystem to: divide a Doppler-frequency spectrum of the received EMsignals into the fourth number of sectors, the sectors representing arespective frequency range within the Doppler-frequency spectrum, asubset of the sectors being equally sized within the Doppler-frequencyspectrum and another subset of the sectors being unequally sized withinthe Doppler-frequency spectrum; and associate each of the channels ofthe received EM signals to a respective sector of the sectors, at leastone of the sectors not being associated with a channel of the receivedEM signals, the association of the channels to the sectors beingconfigured to form an asymmetrical spectrum.

Example 20

A method comprising: transmitting, via multiple transmitters of a radarsystem, electromagnetic (EM) signals in a frequency-divisionmultiplexing (FDM) scheme; receiving, via multiple receivers of theradar system, EM signals reflected by one or more objects; andcontrolling multiple polyphase shifters to introduce a phase shift to atleast one of the transmitted EM signals or the received EM signals, themultiple polyphase shifters being operably connected to the multipletransmitters, the multiple receivers, or a combination thereof, theintroduced phase shift comprising one of at least three potential phaseshifts.

Example 21

A radar system comprising: a first number of receivers configured toreceive EM signals reflected by one or more objects, the EM signalsbeing transmitted by a second number of transmitters in afrequency-division multiplexing (FDM) scheme, the second number beingequal to or not equal to the first number, the received EM signalscomprising a third number of channels, the third number being equal to aproduct of the first number and the second number, at least one of thetransmitted EM signals or the received EM signals including phase shiftsamong the channels; and a processor configured to: divide aDoppler-frequency spectrum of the received EM signals into a fourthnumber of sectors, the sectors representing a respective frequency rangewithin the Doppler-frequency spectrum, the fourth number being equal toor greater than the third number; associate each channel of the receivedEM signals to a respective sector of the sectors; perform, using atleast one channel of the received EM signals, non-coherent integrationon the received EM signals across the sectors; determine, based on thenon-coherent integration, potential detections of the one or moreobjects, the potential detections including one or more actualdetections and one or more aliased detections of the one or moreobjects; determine, based on the potential detections, the actualdetections of the one or more obj ects; and determine, based on theactual detections, a Doppler frequency associated with each of the oneor more objects.

Example 22

The radar system of example 21, wherein: the phase shifts are introducedby the first number of polyphase shifters operably connected to thereceivers.

Example 23

The radar system of example 21, wherein: the phase shifts are introducedby the second number of polyphase shifters being operably connected tothe transmitters.

Example 24

The radar system of example 21, wherein: the phase shifts are introducedby polyphase shifters operably connected to the receivers and thetransmitters.

Example 25

The radar system of any of examples 21 through 24, wherein: the sectorsare equally sized within the Doppler-frequency spectrum; the fourthnumber is equal to or greater than the third number plus one; and eachof the channels of the received EM signals is associated with arespective sector of the sectors, at least one of the sectors not beingassociated with a channel of the received EM signals, the association ofthe channels to the sectors being configured to form an asymmetricalspectrum.

Example 26

The radar system of any of examples 21 through 24, wherein: the sectorsare unequally sized within the Doppler-frequency spectrum; the fourthnumber is equal to the third number; and each of the channels of thereceived EM signals is associated with a respective sector of thesectors, the association of the channels to the unequal sectors beingconfigured to form an asymmetrical spectrum.

Example 27

The radar system of any of examples 21 through 24, wherein: a subset ofthe sectors are equally sized within the Doppler-frequency spectrum andanother subset of the sectors are unequally sized within theDoppler-frequency spectrum; the fourth number is equal to the thirdnumber; and each of the channels of the received EM signals isassociated with a respective sector of the sectors, the association ofthe channels to the sectors being configured to form an asymmetricalspectrum.

Example 28

The radar system of any of examples 21 through 27, wherein the processoris further configured to: determine the potential detections of the oneor more objects by: generating, using a constant-false-alarm-rate (CFAR)threshold, a first logical list of potential detections for a firstchannel of the third number of channels, the potential detectionsincluding one or more peaks within the received EM signals with EMenergy greater than the CFAR threshold, the first logical listrepresenting Doppler bins within the Doppler-frequency spectrum; andperforming, based on the sectors, a particular number of circular shiftson the first logical list of potential detections to generate theparticular number of additional logical lists of potential detections,the particular number being equal to the third number minus one; anddetermine the actual detections of the one or more objects by performinga logical AND operation on the first logical list and additional logicallists of potential detections at each Doppler bin of the logical lists.

Example 29

The radar system any of examples 21 through 27, wherein the processor isfurther configured to: determine the potential detections of the one ormore objects by: generating a first EM spectrum of the received EMsignals for a first channel of the third number of channels; performing,based on the sectors, a particular number of circular shifts on thefirst EM spectrum to generate the particular number of additional EMspectrums of the received EM signals, the particular number being equalto the third number minus one; and determining, across the first andadditional EM spectrums, a minimum EM energy level at each Doppler binof the EM spectrum; and determine the actual detections of the one ormore objects by determining whether the minimum EM energy level at arespective Doppler bin is greater than a constant-false-alarm-rate(CFAR) threshold.

Example 30

The radar system of any of examples 21 through 27, wherein the processoris further configured to: determine the potential detections of the oneor more objects by: generating a first EM spectrum of the received EMsignals for a first channel of the third number of channels; performing,based on the sectors, a particular number of circular shifts on thefirst EM spectrum to generate the particular number of additional EMspectrums of the received EM signals, the particular number being equalto the third number minus one; determining, across the first andadditional EM spectrums, a sum of EM energy levels at each Doppler binof the EM spectrum; and generating, using a constant-false-alarm-rate(CFAR) threshold, a logical list of potential detections, the potentialdetections including one or more peaks within the sum of the EM energylevels with EM energy greater than the CFAR threshold, the logical listrepresenting Doppler bins within the Doppler-frequency spectrum; anddetermine the actual detections of the one or more objects byidentifying the one or more aliased detections based on the associationof each of the channels of the received EM signals to the respectivesector of the sectors.

Example 31

The radar system of example 25, wherein the processor is furtherconfigured to: determine the potential detections of the one or moreobjects by: generating a first EM spectrum of the received EM signalsfor a first channel of the third number of channels; and determining,using the first EM spectrum and for each sector of the fourth number ofsectors, a sector-based integration of EM energy, the sector-basedintegration summing the EM energy of the respective sector and the EMenergy of a particular number of successive sectors, the particularnumber being equal to the third number minus one; and determine theactual detections of the one or more objects by determining a maximum EMenergy level for the sector-based integration of EM energy.

Example 32

The radar system of example 25, wherein the processor is furtherconfigured to: determine the potential detections of the one or moreobjects by: generating a first EM spectrum of the received EM signalsfor a first channel of the third number of channels; performing, basedon the sectors, a particular number of circular shifts on the first EMspectrum to generate the particular number of additional EM spectrums ofthe received EM signals, the particular number being equal to the thirdnumber minus one; and determining, using the first and additional EMspectrums and for each sector of the fourth number of sectors, asector-based integration of EM energy, the sector-based integrationsumming the EM energy of the respective sector across the first andadditional EM spectrums; and determine the actual detections of the oneor more objects by determining a maximum EM energy level for thesector-based integration of EM energy.

Example 33

The radar system of example 25, wherein the processor is furtherconfigured to: determine the potential detections of the one or moreobjects by: generating a first EM spectrum of the received EM signalsfor a first channel of the third number of channels; performing, basedon the sectors, a particular number of circular shifts on the first EMspectrum to generate the particular number of additional EM spectrums ofthe received EM signals, the particular number being equal to the thirdnumber minus one; determining, using the first and additional EMspectrums and for each sector of the fourth number of sectors, asector-based integration of EM energy, the sector-based integrationsumming the EM energy of the respective sector across the first andadditional EM spectrums; determining, across the first and additional EMspectrums, a minimum EM energy level at each Doppler bin of the EMspectrum; generating, using a constant-false-alarm-rate (CFAR) thresholdand the sector-based integration of EM energy, a first logical list ofpotential detections, the first logical list representing Doppler binswithin the Doppler-frequency spectrum; and generating, using the CFARthreshold and the minimum EM energy level at each Doppler bin of the EMspectrum, a second logical list of potential detections; and determinethe actual detections of the one or more objects by performing a logicalAND operation on the first and second logical lists of potentialdetections at each Doppler bin.

Example 34

The radar system of any of examples 21 through 33, wherein thetransmitters and the receivers operate as part of a multiple-input andmultiple-output (MIMO) radar approach.

Example 35

The radar system of any of examples 21 through 34, wherein the radarsystem is configured to be installed on an automobile.

Example 36

A computer-readable storage media comprising computer-executableinstructions that, when executed, cause a processor of a radar systemto: receive, via a first number of receivers, EM signals reflected byone or more obj ects, the EM signals transmitted by a second number oftransmitters in a frequency-division multiplexing (FDM) scheme, thesecond number being equal to or not equal to the first number, thereceived EM signals comprising a third number of channels, the thirdnumber being equal to a product of the first number and the secondnumber, at least one of the transmitted EM signals or the received EMsignals including phase shifts among the channels; divide aDoppler-frequency spectrum of the received EM signals into a fourthnumber of sectors, the sectors representing a respective frequency rangewithin the Doppler-frequency spectrum, the fourth number being equal toor greater than the third number; associate each channel of the receivedEM signals to a respective sector of the sectors; perform, using atleast one channel of the received EM signals, non-coherent integrationon the received EM signals across the sectors; determine, based on thenon-coherent integration, potential detections of the one or moreobjects, the potential detections including one or more actualdetections and one or more aliased detections of the one or moreobjects; determine, based on the potential detections, the actualdetections of the one or more objects; and determine, based on theactual detections, a Doppler frequency associated with each of the oneor more objects.

Example 37

The computer-readable storage media of example 36, wherein: the sectorsare equally sized within the Doppler-frequency spectrum; the fourthnumber is equal to or greater than the third number plus one; each ofthe channels of the received EM signals is associated with a respectivesector of the sectors, at least one of the sectors not being associatedwith a channel of the received EM signals, the association of thechannels to the sectors being configured to form an asymmetricalspectrum; and the computer-readable storage media comprisescomputer-executable instructions that, when executed, further cause theprocessor of a radar system to: determine the potential detections ofthe one or more objects by: generating a first EM spectrum of thereceived EM signals for a first channel of the third number of channels;and determining, using the first EM spectrum and for each sector of thefourth number of sectors, a sector-based integration of EM energy, thesector-based integration summing the EM energy of the respective sectorand the EM energy of a particular number of successive sectors, theparticular number being equal to the third number minus one; anddetermine the actual detections of the one or more objects bydetermining a maximum EM energy level for the sector-based integrationof EM energy.

Example 38

The computer-readable storage media of example 36, wherein: the sectorsare equally sized within the Doppler-frequency spectrum; the fourthnumber is equal to or greater than the third number plus one; each ofthe channels of the received EM signals is associated with a respectivesector of the sectors, at least one of the sectors not being associatedwith a channel of the received EM signals, the association of thechannels to the sectors being configured to form an asymmetricalspectrum; and the computer-readable storage media comprisescomputer-executable instructions that, when executed, further cause theprocessor of a radar system to: determine the potential detections ofthe one or more objects by: generating a first EM spectrum of thereceived EM signals for a first channel of the third number of channels;performing, based on the sectors, a particular number of circular shiftson the first EM spectrum to generate the particular number of additionalEM spectrums of the received EM signals, the particular number beingequal to the third number minus one; and determining, using the firstand additional EM spectrums and for each sector of the fourth number ofsectors, a sector-based integration of EM energy, the sector-basedintegration summing the EM energy of the respective sector across thefirst and additional EM spectrums; and determine the actual detectionsof the one or more objects by determining a maximum EM energy level forthe sector-based integration of EM energy.

Example 39

The computer-readable storage media of example 36, wherein: the sectorsare equally sized within the Doppler-frequency spectrum; the fourthnumber is equal to or greater than the third number plus one; each ofthe channels of the received EM signals is associated with a respectivesector of the sectors, at least one of the sectors not being associatedwith a channel of the received EM signals, the association of thechannels to the sectors being configured to form an asymmetricalspectrum; and the computer-readable storage media comprisescomputer-executable instructions that, when executed, further cause theprocessor of a radar system to: determine the potential detections ofthe one or more objects by: generating a first EM spectrum of thereceived EM signals for a first channel of the third number of channels;performing, based on the sectors, a particular number of circular shiftson the first EM spectrum to generate the particular number of additionalEM spectrums of the received EM signals, the particular number beingequal to the third number minus one; determining, using the first andadditional EM spectrums and for each sector of the fourth number ofsectors, a sector-based integration of EM energy, the sector-basedintegration summing the EM energy of the respective sector across thefirst and additional EM spectrums; determining, across the first andadditional EM spectrums, a minimum EM energy level at each Doppler binof the EM spectrum; generating, using a constant-false-alarm-rate (CFAR)threshold and the sector-based integration of EM energy, a first logicallist of potential detections, the first logical list representingDoppler bins within the Doppler-frequency spectrum; and generating,using the CFAR threshold and the minimum EM energy level at each Dopplerbin of the EM spectrum, a second logical list of potential detections;and determine the actual detections of the one or more objects byperforming a logical AND operation on the first and second logical listsof potential detections at each Doppler bin.

Example 40

A method comprising: receiving, via a first number of receivers, EMsignals reflected by one or more objects, the EM signals transmitted bya second number of transmitters in a frequency-division multiplexing(FDM) scheme, the second number being equal to or not equal to the firstnumber, the received EM signals comprising a third number of channels,the third number being equal to a product of the first number and thesecond number, at least one of the transmitted EM signals or thereceived EM signals including phase shifts among the channels; dividinga Doppler-frequency spectrum of the received EM signals into a fourthnumber of sectors, the sectors representing a respective frequency rangewithin the Doppler-frequency spectrum, the fourth number being equal toor greater than the third number; associating each channel of thereceived EM signals to a respective sector of the sectors; performing,using at least one channel of the received EM signals, non-coherentintegration on the received EM signals across the sectors; determining,based on the non-coherent integration, potential detections of the oneor more objects, the potential detections including one or more actualdetections and one or more aliased detections of the one or moreobjects; determining, based on the potential detections, the actualdetections of the one or more objects; and determining, based on theactual detections, a Doppler frequency associated with each of the oneor more objects.

CONCLUSION

While various embodiments of the disclosure are described in theforegoing description and shown in the drawings, it is to be understoodthat this disclosure is not limited thereto but may be variouslyembodied to practice within the scope of the following claims. From theforegoing description, it will be apparent that various changes may bemade without departing from the scope of the disclosure as defined bythe following claims.

What is claimed is:
 1. A radar system comprising: a first number ofreceivers configured to receive EM signals reflected by one or moreobjects, the EM signals being transmitted by a second number oftransmitters in a frequency-division multiplexing (FDM) scheme, thesecond number being equal to or not equal to the first number, thereceived EM signals comprising a third number of channels, the thirdnumber being equal to a product of the first number and the secondnumber, at least one of the transmitted EM signals or the received EMsignals including phase shifts among the channels; and a processorconfigured to: divide a Doppler-frequency spectrum of the received EMsignals into a fourth number of sectors, the sectors representing arespective frequency range within the Doppler-frequency spectrum, thefourth number being equal to or greater than the third number; associateeach channel of the received EM signals to a respective sector of thesectors; perform, using at least one channel of the received EM signals,non-coherent integration on the received EM signals across the sectors;determine, based on the non-coherent integration, potential detectionsof the one or more objects, the potential detections including one ormore actual detections and one or more aliased detections of the one ormore objects; determine, based on the potential detections, the actualdetections of the one or more objects; and determine, based on theactual detections, a Doppler frequency associated with each of the oneor more objects.
 2. The radar system of claim 1, wherein: the phaseshifts are introduced by the first number of polyphase shifters operablyconnected to the receivers.
 3. The radar system of claim 1, wherein: thephase shifts are introduced by the second number of polyphase shiftersbeing operably connected to the transmitters.
 4. The radar system ofclaim 1, wherein: the phase shifts are introduced by polyphase shiftersoperably connected to the receivers and the transmitters.
 5. The radarsystem of claim 1, wherein: the sectors are equally sized within theDoppler-frequency spectrum; the fourth number is equal to or greaterthan the third number plus one; and each of the channels of the receivedEM signals is associated with a respective sector of the sectors, atleast one of the sectors not being associated with a channel of thereceived EM signals, the association of the channels to the sectorsbeing configured to form an asymmetrical spectrum.
 6. The radar systemof claim 1, wherein: the sectors are unequally sized within theDoppler-frequency spectrum; the fourth number is equal to the thirdnumber; and each of the channels of the received EM signals isassociated with a respective sector of the sectors, the association ofthe channels to the unequal sectors being configured to form anasymmetrical spectrum.
 7. The radar system of claim 1, wherein: a subsetof the sectors are equally sized within the Doppler-frequency spectrumand another subset of the sectors are unequally sized within theDoppler-frequency spectrum; the fourth number is equal to the thirdnumber; and each of the channels of the received EM signals isassociated with a respective sector of the sectors, the association ofthe channels to the sectors being configured to form an asymmetricalspectrum.
 8. The radar system of claim 1, wherein the processor isfurther configured to: determine the potential detections of the one ormore objects by: generating, using a constant-false-alarm-rate (CFAR)threshold, a first logical list of potential detections for a firstchannel of the third number of channels, the potential detectionsincluding one or more peaks within the received EM signals with EMenergy greater than the CFAR threshold, the first logical listrepresenting Doppler bins within the Doppler-frequency spectrum; andperforming, based on the sectors, a particular number of circular shiftson the first logical list of potential detections to generate theparticular number of additional logical lists of potential detections,the particular number being equal to the third number minus one; anddetermine the actual detections of the one or more objects by performinga logical AND operation on the first logical list and additional logicallists of potential detections at each Doppler bin of the logical lists.9. The radar system of claim 1, wherein the processor is furtherconfigured to: determine the potential detections of the one or moreobjects by: generating a first EM spectrum of the received EM signalsfor a first channel of the third number of channels; performing, basedon the sectors, a particular number of circular shifts on the first EMspectrum to generate the particular number of additional EM spectrums ofthe received EM signals, the particular number being equal to the thirdnumber minus one; and determining, across the first and additional EMspectrums, a minimum EM energy level at each Doppler bin of the EMspectrum; and determine the actual detections of the one or more objectsby determining whether the minimum EM energy level at a respectiveDoppler bin is greater than a constant-false-alarm-rate (CFAR)threshold.
 10. The radar system of claim 1, wherein the processor isfurther configured to: determine the potential detections of the one ormore objects by: generating a first EM spectrum of the received EMsignals for a first channel of the third number of channels; performing,based on the sectors, a particular number of circular shifts on thefirst EM spectrum to generate the particular number of additional EMspectrums of the received EM signals, the particular number being equalto the third number minus one; determining, across the first andadditional EM spectrums, a sum of EM energy levels at each Doppler binof the EM spectrum; and generating, using a constant-false-alarm-rate(CFAR) threshold, a logical list of potential detections, the potentialdetections including one or more peaks within the sum of the EM energylevels with EM energy greater than the CFAR threshold, the logical listrepresenting Doppler bins within the Doppler-frequency spectrum; anddetermine the actual detections of the one or more objects byidentifying the one or more aliased detections based on the associationof each of the channels of the received EM signals to the respectivesector of the sectors.
 11. The radar system of claim 5, wherein theprocessor is further configured to: determine the potential detectionsof the one or more objects by: generating a first EM spectrum of thereceived EM signals for a first channel of the third number of channels;and determining, using the first EM spectrum and for each sector of thefourth number of sectors, a sector-based integration of EM energy, thesector-based integration summing the EM energy of the respective sectorand the EM energy of a particular number of successive sectors, theparticular number being equal to the third number minus one; anddetermine the actual detections of the one or more objects bydetermining a maximum EM energy level for the sector-based integrationof EM energy.
 12. The radar system of claim 5, wherein the processor isfurther configured to: determine the potential detections of the one ormore objects by: generating a first EM spectrum of the received EMsignals for a first channel of the third number of channels; performing,based on the sectors, a particular number of circular shifts on thefirst EM spectrum to generate the particular number of additional EMspectrums of the received EM signals, the particular number being equalto the third number minus one; and determining, using the first andadditional EM spectrums and for each sector of the fourth number ofsectors, a sector-based integration of EM energy, the sector-basedintegration summing the EM energy of the respective sector across thefirst and additional EM spectrums; and determine the actual detectionsof the one or more objects by determining a maximum EM energy level forthe sector-based integration of EM energy.
 13. The radar system of claim5, wherein the processor is further configured to: determine thepotential detections of the one or more objects by: generating a firstEM spectrum of the received EM signals for a first channel of the thirdnumber of channels; performing, based on the sectors, a particularnumber of circular shifts on the first EM spectrum to generate theparticular number of additional EM spectrums of the received EM signals,the particular number being equal to the third number minus one;determining, using the first and additional EM spectrums and for eachsector of the fourth number of sectors, a sector-based integration of EMenergy, the sector-based integration summing the EM energy of therespective sector across the first and additional EM spectrums;determining, across the first and additional EM spectrums, a minimum EMenergy level at each Doppler bin of the EM spectrum; generating, using aconstant-false-alarm-rate (CFAR) threshold and the sector-basedintegration of EM energy, a first logical list of potential detections,the first logical list representing Doppler bins within theDoppler-frequency spectrum; and generating, using the CFAR threshold andthe minimum EM energy level at each Doppler bin of the EM spectrum, asecond logical list of potential detections; and determine the actualdetections of the one or more objects by performing a logical ANDoperation on the first and second logical lists of potential detectionsat each Doppler bin.
 14. The radar system of claim 1, wherein thetransmitters and the receivers operate as part of a multiple-input andmultiple-output (MIMO) radar approach.
 15. The radar system of claim 1,wherein the radar system is configured to be installed on an automobile.16. A computer-readable storage media comprising computer-executableinstructions that, when executed, cause a processor of a radar systemto: receive, via a first number of receivers, EM signals reflected byone or more objects, the EM signals transmitted by a second number oftransmitters in a frequency-division multiplexing (FDM) scheme, thesecond number being equal to or not equal to the first number, thereceived EM signals comprising a third number of channels, the thirdnumber being equal to a product of the first number and the secondnumber, at least one of the transmitted EM signals or the received EMsignals including phase shifts among the channels; divide aDoppler-frequency spectrum of the received EM signals into a fourthnumber of sectors, the sectors representing a respective frequency rangewithin the Doppler-frequency spectrum, the fourth number being equal toor greater than the third number; associate each channel of the receivedEM signals to a respective sector of the sectors; perform, using atleast one channel of the received EM signals, non-coherent integrationon the received EM signals across the sectors; determine, based on thenon-coherent integration, potential detections of the one or moreobjects, the potential detections including one or more actualdetections and one or more aliased detections of the one or moreobjects; determine, based on the potential detections, the actualdetections of the one or more objects; and determine, based on theactual detections, a Doppler frequency associated with each of the oneor more objects.
 17. The computer-readable storage media of claim 16,wherein: the sectors are equally sized within the Doppler-frequencyspectrum; the fourth number is equal to or greater than the third numberplus one; each of the channels of the received EM signals is associatedwith a respective sector of the sectors, at least one of the sectors notbeing associated with a channel of the received EM signals, theassociation of the channels to the sectors being configured to form anasymmetrical spectrum; and the computer-readable storage media comprisescomputer-executable instructions that, when executed, further cause theprocessor of a radar system to: determine the potential detections ofthe one or more objects by: generating a first EM spectrum of thereceived EM signals for a first channel of the third number of channels;and determining, using the first EM spectrum and for each sector of thefourth number of sectors, a sector-based integration of EM energy, thesector-based integration summing the EM energy of the respective sectorand the EM energy of a particular number of successive sectors, theparticular number being equal to the third number minus one; anddetermine the actual detections of the one or more objects bydetermining a maximum EM energy level for the sector-based integrationof EM energy.
 18. The computer-readable storage media of claim 16,wherein: the sectors are equally sized within the Doppler-frequencyspectrum; the fourth number is equal to or greater than the third numberplus one; each of the channels of the received EM signals is associatedwith a respective sector of the sectors, at least one of the sectors notbeing associated with a channel of the received EM signals, theassociation of the channels to the sectors being configured to form anasymmetrical spectrum; and the computer-readable storage media comprisescomputer-executable instructions that, when executed, further cause theprocessor of a radar system to: determine the potential detections ofthe one or more objects by: generating a first EM spectrum of thereceived EM signals for a first channel of the third number of channels;performing, based on the sectors, a particular number of circular shiftson the first EM spectrum to generate the particular number of additionalEM spectrums of the received EM signals, the particular number beingequal to the third number minus one; and determining, using the firstand additional EM spectrums and for each sector of the fourth number ofsectors, a sector-based integration of EM energy, the sector-basedintegration summing the EM energy of the respective sector across thefirst and additional EM spectrums; and determine the actual detectionsof the one or more objects by determining a maximum EM energy level forthe sector-based integration of EM energy.
 19. The computer-readablestorage media of claim 16, wherein: the sectors are equally sized withinthe Doppler-frequency spectrum; the fourth number is equal to or greaterthan the third number plus one; each of the channels of the received EMsignals is associated with a respective sector of the sectors, at leastone of the sectors not being associated with a channel of the receivedEM signals, the association of the channels to the sectors beingconfigured to form an asymmetrical spectrum; and the computer-readablestorage media comprises computer-executable instructions that, whenexecuted, further cause the processor of a radar system to: determinethe potential detections of the one or more objects by: generating afirst EM spectrum of the received EM signals for a first channel of thethird number of channels; performing, based on the sectors, a particularnumber of circular shifts on the first EM spectrum to generate theparticular number of additional EM spectrums of the received EM signals,the particular number being equal to the third number minus one;determining, using the first and additional EM spectrums and for eachsector of the fourth number of sectors, a sector-based integration of EMenergy, the sector-based integration summing the EM energy of therespective sector across the first and additional EM spectrums;determining, across the first and additional EM spectrums, a minimum EMenergy level at each Doppler bin of the EM spectrum; generating, using aconstant-false-alarm-rate (CFAR) threshold and the sector-basedintegration of EM energy, a first logical list of potential detections,the first logical list representing Doppler bins within theDoppler-frequency spectrum; and generating, using the CFAR threshold andthe minimum EM energy level at each Doppler bin of the EM spectrum, asecond logical list of potential detections; and determine the actualdetections of the one or more objects by performing a logical ANDoperation on the first and second logical lists of potential detectionsat each Doppler bin.
 20. A method comprising: receiving, via a firstnumber of receivers, EM signals reflected by one or more obj ects, theEM signals transmitted by a second number of transmitters in afrequency-division multiplexing (FDM) scheme, the second number beingequal to or not equal to the first number, the received EM signalscomprising a third number of channels, the third number being equal to aproduct of the first number and the second number, at least one of thetransmitted EM signals or the received EM signals including phase shiftsamong the channels; dividing a Doppler-frequency spectrum of thereceived EM signals into a fourth number of sectors, the sectorsrepresenting a respective frequency range within the Doppler-frequencyspectrum, the fourth number being equal to or greater than the thirdnumber; associating each channel of the received EM signals to arespective sector of the sectors; performing, using at least one channelof the received EM signals, non-coherent integration on the received EMsignals across the sectors; determining, based on the non-coherentintegration, potential detections of the one or more objects, thepotential detections including one or more actual detections and one ormore aliased detections of the one or more objects; determining, basedon the potential detections, the actual detections of the one or moreobjects; and determining, based on the actual detections, a Dopplerfrequency associated with each of the one or more objects.